The present disclosure relates to rotating electrical machines.
Conventionally, rotating electrical machines are known which include concentric coils of the same phase connected in parallel with each other.
A plurality of concentric coils (e.g., first to fourth round wire concentric coils) formed by concentrically winding a round wire and connected in parallel with each other are conventionally known in the art. Each of the first to fourth round wire concentric coils includes a plurality of coils (hereinafter referred to as the coil portions) connected in series with each other. The first to fourth round wire concentric coils are placed in slots of a stator core in order of the plurality of coil portions of the first round wire concentric coil, the plurality of coil portions of the second round wire concentric coil, the plurality of coil portions of the third round wire concentric coil, and the plurality of coil portions of the fourth round wire concentric coil (namely, the coils are wound around adjacent poles).
For example, in the case where the central axis of a rotor is not aligned with the central axis of a stator, the positional relationship between each permanent magnet placed in the rotor and each of the first to fourth round wire concentric coils may be imbalanced. In this case, a circulating current flows in the concentric coil, which results in generation of noise and vibration, etc.
In order to overcome this disadvantage, one of the coil portions of the first round wire concentric coil, one of the coil portions of the second round wire concentric coil, one of the coil portions of the third round wire concentric coil, and one of the coil portions of the fourth round wire concentric coil are conventionally placed in this order in the slots of the stator core (namely, the coils are wound around every other pole). This eliminates the imbalance in the positional relationship between each permanent magnet and each of the first to fourth round wire concentric coils and thus reduces generation of noise and vibration due to a circulating current in the concentric coil.
Conventionally, rotating electrical machines are also known which include a concentric coil formed by concentrically winding a rectangular wire. Such a rotating electrical machine is disclosed in, e.g., Japanese Patent Application Publication No. 2012-125043 (JP 2012-125043 A).
JP 2012-125043 A discloses a motor including a first concentric coil and a second concentric coil which are formed by concentrically winding a rectangular wire. The first concentric coil is formed by winding a rectangular wire so as to create a clearance between adjacent ones of the turns of the rectangular wire so that the rectangular wire of the second concentric coil can be inserted in the clearances. That is, in JP 2012-125043 A, portions of the rectangular wire of the first concentric coil and portions of the rectangular wire of the second concentric coil are alternately placed in each slot of a stator core in the radial direction of the stator core.
In the motor of JP 2012-125043 A, however, since the rectangular wire of the first concentric coil and the rectangular wire of the second concentric coil are mixedly present in each slot, it is difficult to wind the coils around every other pole in order to eliminate an imbalance in the positional relationship between each permanent magnet and each of the first and second concentric coils. It is therefore desired to reduce noise and vibration due to a circulating current in a concentric coil in rotating electrical machines including a concentric coil formed by concentrically winding a rectangular wire.
An exemplary aspect of the present disclosure provides a rotating electrical machine that includes a concentric coil formed by concentrically winding a rectangular wire and that can reduce generation of noise and vibration due to a circulating current in the concentric coil.
A rotating electrical machine according to one exemplary aspect of the present disclosure includes: a rotor core having a permanent magnet placed therein; a stator core placed so as to face the rotor core in a radial direction and having a plurality of slots; and a concentric coil formed by concentrically winding a rectangular wire and placed in the slots of the stator core. The concentric coil includes a first concentric coil, a second concentric coil, a third concentric coil, and a fourth concentric coil which are of the same phase and are connected in parallel with each other. Each of the first concentric coil, the second concentric coil, the third concentric coil, and the fourth concentric coil has a one-side concentric coil whose coil center is located on one side in a circumferential direction with respect to a center of a magnetic pole, and an other-side concentric coil whose coil center is located on the other side in the circumferential direction with respect to a center of a magnetic pole.
In the rotating electrical machine according to the exemplary aspect of the present disclosure, as described above, each of the first concentric coil, the second concentric coil, the third concentric coil, and the fourth concentric coil has the one-side concentric coil whose coil center is located on the one side in the circumferential direction with respect to the center of the magnetic pole, and the other-side concentric coil whose coil center is located on the other side in the circumferential direction with respect to the center of the magnetic pole. This prevents the concentric coil from being unevenly placed only on the one side or the other side in the circumferential direction with respect to the center of the magnetic pole, and thus can eliminate an imbalance in the positional relationship between the permanent magnet and the concentric coil. As a result, generation of noise and vibration due to a circulating current in the concentric coil can be reduced in the rotating electrical machine including the concentric coil formed by concentrically winding a rectangular wire. Adverse effects on torque of the rotating electrical machine due to the circulating current in the concentric coil can also be reduced.
According to the present disclosure, as described above, generation of noise and vibration due to a circulating current in a concentric coil can be reduced in a rotating electrical machine including a concentric coil formed by concentrically winding a rectangular wire.